(1) Field of the Invention
The present invention relates to apparatus for determining the dynamic mechanical properties of an electro-rheological (ER) fluid as a function of frequency, voltage, and temperature. The measured properties can then be used to characterize the effectiveness and behavior of the ER fluids for various engineering applications.
(2) Description of the Prior Art
Most ER fluid test methods do not allow for property characterization as a function of high frequencies or temperature. They may be limited to low frequency static testing. There has been limited dynamic testing up to 200 Hz using a flexural beam apparatus. This technique has disadvantages in that it must be fabricated by sandwiching the fluid between two metal plates that will act as the electrodes and sealing all the edges with a leak proof sealant. This technique is difficult, time consuming and messy.
A number of patented constructions typify the prior art. For example, U.S. Pat. No. 4,437,337 to Fenrick discloses a viscoelastometer for measuring a viscoelastic effect in a liquid. A liquid sample cup, in association with a pneumatic cylinder, is moved at a selected rate between an upper and lower position. A rigid member is immersed in the liquid when the sample cup is in the upper position. As the cup moves toward its lower position, the liquid forms a filament between the rigid member and the surface of the liquid. As the rigid member moves away from the liquid surface, the liquid relaxes and separates from the rigid member as a function of the viscosity and elasticity of the fluid.
In another instance, U.S. Pat. No. 4,648,263 to Deysarkar et al discloses a centering support attachment for a viscometer which has a rotating head placed in a stationary container of liquid being tested.
U.S. Pat. No. 4,862,735 to Williams et al discloses a viscometer which, in operation, oscillates a probe within a container filled with a fluid specimen. Strain gages are mounted on a lever connected to the probe for measuring shear forces experienced by the probe a it oscillates.
It was with knowledge of the prior art as just described that the present invention was conceived and has now been reduced to practice.